1. Field of the Invention
This invention relates to a damper disc for use in a lockup clutch of an automotive torque converter or the like and, more particularly, to improvements in the construction of a retainer plate in such damper disk for holding a damper spring in position.
2. Description of the Prior Art
A damper disk of the type to which the invention is directed is described in Japanese Utility Model Application No. 61-170593 filed by the present applicant. The damper disc includes an input plate (a piston) fitted with an input friction facing, an output plate securely fixed to a turbine (a turbine shell or turbine hub), a damper spring (a coil spring) for interconnecting the two plates, and a retainer plate for holding the spring in position.
The retainer plate is securely fixed to the input plate and has a connector (a pawl) connecting circumferentially to one end of the spring. Therefore, the input plate is connected to the spring through the retainer plate. The retainer plate is adapted to perform a function to radially retain the spring and, to this end, it has a partially cylindrical inner support portion extending along the inner periphery of the spring and a partially cylindrical outer support portion extending along the outer periphery of the spring. Further, a cylindrical portion is provided on the outer periphery of the input plate, and the above mentioned outer support portion extends into the cylindrical portion.
According to this arrangement, when the spring begins to move radially outwardly under centrifugal force during engine operation, the outer support portion supports the spring in position to prevent it from making such movement thereby to stabilize the posture of the spring so that the spring can be allowed to perform its required operation. In this process of operation, the outer support portion is supported with respect to its outer periphery by means of the cylindrical portion of the input plate and is accordingly prevented from being substantially deformed radially by the centrifugal force from the spring.
However, the retainer plate is highly rigid because it has been subjected to hardening treatment, and the input plate also has high rigidity; and therefore in the stage of assembling it is difficult to elastically deform the plates thereby to allow the retainer plate to be brought into assembly with the input plate. As such, when possible dimensional errors with respect to the two plates are considered, it is necessary that, in the stage of assembly work, the outer diameter of the outer support portion of the retainer plate be set slightly smaller than the inner diameter of the outer peripheral cylindrical portion of the input plate in order to allow the outer support portion to be fitted in the outer peripheral cylindrical portion. Therefore, a slight clearance is created between the support portion and the cylindrical portion, so that when the support portion is subjected to the centrifugal force from the spring as above noted, the support portion will be radially outwardly deformed by an amount equivalent to the clearance with the result that a crack may be caused to the retainer plate.
The object of the invention is to provide a retainer plate construction which solves the foregoing problem.